Shaft bearing retainer

ABSTRACT

A retainer for holding bearings within a shaft bearing has C-shaped pockets for holding the bearings. Between the pockets are connecting portions, which are close to the openings of the pockets. The rear sides of adjacent pockets and the rear side of the connecting portion for the adjacent pockets form a concave site that is deeply gouged into the retainer. The bottom of the concave site is closer to the openings than the bottom of the pockets, thereby allowing base oil from grease in the concave site to better migrate onto the bearings and so lubricate the shaft bearing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent ApplicationSerial Number 2002-319668 entitled “Shaft Bearing Retainer,” naming thesame inventor, filed on Nov. 1, 2002, claiming priority benefits under35 U.S.C. §119.

FIELD OF THE INVENTION

The present invention relates to shaft bearings that include bearings.More particularly, the present invention relates to retainers forholding the bearings in the shaft bearing.

BACKGROUND OF THE INVENTION

Shaft bearings are used to constrain a rotating shaft to maintain itsaxis of rotation. Such shaft bearings are used in motors, such asspindle motors, commonly found in computer equipment and audio systems.A typical structure for a shaft bearing includes two rings, bearings,and a retainer. The two rings are an inner ring, having a rotationgroove on its outer surface, and an outer ring, having a correspondingrotation groove on its inner surface. The grooves and the axis ofrotation are common to the rings. Between the two rotation grooves are aplurality of bearings, sometimes called ball bearings, which are evenlyspaced apart circumferentially. The retainer is between the inner andouter rings and maintains even spacing of the bearings around thecircumference of the rings. In this manner, the inner ring rotates withrespect to the outer ring along a common axis by means of the evenlyspaced apart bearings between the rotation grooves.

One type of retainer is a crown retainer. A crown retainer is typicallymolded from resin into a ring shape and includes a plurality of pocketsequidistantly spaced around the circumference of the retainer. Eachpocket retains a corresponding bearing to maintain the even spacing ofthe bearings around the rotation grooves. The pockets are open on oneside of the retainer along the axial direction of the retainer. Theinner surface of each pocket has a curvature corresponding to thecurvature of the bearing.

The shaft bearing is assembled by inserting the bearings between therespective rotation grooves of the outer and inner rings, and insertingthe retainer between the rings to snap each bearing into itscorresponding pocket on the retainer. Upon mounting the retainer, greaseis inserted into the shaft bearing, and a shield is mounted on the shaftbearing to close the gap between the inner and outer rings.

The grease is inserted onto the retainer between the inner and outerrings. The grease is inserted from the side of the retainer that has thepocket openings, and it is inserted onto the edge faces of the retainerbetween the pockets, where it adheres. A component of the grease is alow viscosity lubricating oil, called base oil, which soaks through fromthe grease and flows into the pockets as the retainer revolves aroundthe axis of rotation. Since the bearings rotate in the retainer, thebase oil in the interior of the pockets migrates between the rotationgrooves of the inner and outer rings. In this manner, the base oillubricates the rotation faces of the bearings in contact with therotation grooves.

Some shaft bearings, however, do not allow insertion of the grease fromthe side of the retainer having the pocket opening. Examples of suchshaft bearings have multiple coaxial rows of bearings. One such exampleis a shaft bearing having two coaxial rows of bearings between the innerand outer rings. Each row of bearings has a respective retainer that isinserted between the rings to snap the two rows of bearings into place.But the pocket openings of the two retainers face each other in thisassembly. Access to the retainers is only to the respective sides of theretainers that are opposite to the pocket openings. As such, the greaseis not near the pockets as they move around the circumference of thegrooves, and it takes a relatively long time for sufficient base oil toreach the surface of the bearings.

In this case, the lack of sufficient lubrication reduces the life spanof the shaft bearing or renders the shaft bearing immediately unusable.Moreover, the grease immediately scatters when the shaft begins torotate and adheres to the outer ring and shield. Achieving a stablerotation with low torque is therefore difficult.

One proposed solution is to include channels between the pockets on theouter circumference of the retainer. Each channel runs between the edgefaces of the retainer. Either the channel holds the grease or the greaseis inserted through the channel to the pocket opening side of theretainer. Even so, it is difficult to align the nozzle of a grease gunwith each channel, and the grease would adhere to the inner surface ofthe outer ring and not sufficiently utilize the channel.

A further proposed solution to the problems associated with the channelsin the retainer is to form a relatively elongated nozzle access areathat leads to each channel on the edge face opposite the pocket opening.Such a nozzle access area is described in Japanese Patent PublicationNo. JP 8-277843. The ejection opening of the nozzle may be easilypositioned with respect to this relatively long nozzle access area, incontrast to the difficulty of positioning the nozzle with respect to thechannels as described above. The easy positioning allows for theadequate insertion of grease.

Since grease is inserted from the nozzle access area up to the channel,however, this solution is inefficient because not all of the grease isused. Also, flow resistance of the grease is generated as the routetraveled by the inserted grease lengthens, and the channel may still notreceive sufficient grease.

SUMMARY

A retainer for a shaft bearing is described below to address the needfor a retainer that allows base oil to reach pocket openings on theretainer, where the base oil is from grease that is applied to the edgeface of the retainer opposite the pocket openings.

One aspect of the shaft bearing retainer includes at least two pocketrings. Each pocket ring has a circumferential outer surface and anopening. The shaft bearing retainer also includes at least oneconnecting portion disposed between the two pocket rings. The connectingportion is located in close proximity to the openings of the pocketrings, and the connecting portion and circumferential outer surfaces ofthe pocket rings form a concave site.

Another aspect of the invention is a shaft bearing. The shaft bearingincludes a retainer which has at least two pocket rings. Each pocketring has a circumferential outer surface and an opening. The retaineralso includes at least one connecting portion disposed between the twopocket rings. The connecting portion is located in close proximity tothe openings of the pocket rings, and the connecting portion andcircumferential outer surfaces of the pocket rings form a concave site.

The foregoing and other features and advantages of preferred embodimentswill be more readily apparent from the following detailed description,which proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view illustrating a shaftbearing containing a retainer;

FIG. 2 is an overall perspective view of a preferred embedment of theretainer of FIG. 1;

FIG. 3 is a partial magnified side view of a preferred embodiment of theretainer of FIG. 1;

FIG. 4 is a partial magnified side view of another preferred embodimentof the retainer of FIG. 1; and

FIG. 5 is a partial magnified view of yet another preferred embodimentof the retainer of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a longitudinal cross section of a shaft bearing 20 thatincludes a shaft 10, which rotates. The shaft bearing 20 includes anouter ring 30, an inner ring 40, two rows of rolling elements such asbearings 50, and a ring-shaped retainer 60 that holds the bearings 50 ineach row. The shaft 10 has a stepped shape, having a large diameterportion 10A and a small diameter portion 10B that are coaxial to eachother. The outer circumferential face of the large diameter portion 10Ahas a rotation groove 11 along the direction of the circumference. Theouter circumferential face of the small diameter portion 10B, has aninner ring 40 affixed by means such as adhesive. The external diameterof the inner ring 40 equals the external diameter of the large diameterportion 10A of the shaft 10. The outer circumferential face of the innerring 40 has a rotation groove 41 along the direction of thecircumference. The inner circumference face of the outer ring 30 has tworows of rotation grooves 31 formed along the direction of thecircumference.

Between each rotation groove 31 of the outer ring 30 and the respectiverotation grooves 11, 41 of the shaft 10 and the inner ring 40, is aprescribed number of bearings 50, which are held at equal intervals inthe direction of the circumference. The bearings 50 are snapped into theretainers 60 and roll freely. Shields 51 close the spacing of both endportions of the shaft bearing 20 after grease is inserted into eachretainer. The shields 51 are mounted on the inner circumferential faceof the outer ring 30 by snap rings 52. In this shaft bearing 20, thelarge diameter portion 10A of the shaft 10 is constrained by the outerring 30 by means of bearings 50 and rotates freely. The small diameterportion 10B is constrained by the outer ring 30 by means of the innerring 40 and the bearings 50.

The shaft bearing 20 is assembled in the following manner. The innerring 40 is snapped into the small diameter portion 10B of the shaft 10.The shaft 10 is inserted into the outer ring 30 and the prescribednumber of bearings 50 are snapped in between the respective rotationgrooves 11 and 41 of the shaft 10 and the inner ring 40. The retainer 60is snapped onto the bearings 50, and the inner ring 40 is adhered to theshaft 10. After assembly, the shield 51 is mounted with the snap ring52.

FIG. 2 is an overall perspective view of the retainer 60 in the shaftbearing 20 of FIG. 1. The retainer is a crown type composed of resin orother such deformable elastomeric material. It should be understood,however, that the present invention is not restricted to resin and thatother deformable elastomeric material may be used such as polypropylene,rubber, or polyethylene. The retainer 60 includes a plurality of pocketrings 70 disposed at equal intervals along the direction of thecircumference of the retainer 60. Connecting portions 80 are disposedbetween these pocket rings 70, connecting the pocket rings.

The pocket ring 70 is C-shaped. The inner portion of the pocket ring 70is formed by the pocket 72, into which the bearings 50 are snapped. Anopening 72 b of the pocket 72 is open on one of the sides of the pocket72 in the direction along the axial direction of the shaft retainer 60.The opening 72 b of the pocket 72 is the space between both edges of thepocket rings 70. The pocket ring 70 includes a pair of nail portions 71which may deform elastically on either side of the pocket opening 72 bin preference to deformation of the connecting portion 80. The pocketopening 72 b is the space between the nail portions 71. The internalface of the pocket 72 has a curved surface corresponding the surface ofthe bearing 50 that is snapped into the retainer 60. The bearings 50 areinserted into the retainer 60 by placing the bearing 50 in contact withthe tips of the nail portions 71. Each nail portion 71 elasticallydeforms and widens to accept the bearing 50. By further insertion, thebearing 50 snaps into the pocket 72. In this manner, each bearing 50 isheld at equal intervals along the circumference of the retainer 60.

FIG. 3 is a partial magnified side view of a preferred embodiment of theretainer 60. The rear face side of the retainer 60 is defined as theside opposite to those of the pocket openings 72 b. On the rear faceside are concave sites 61, formed between adjacent pocket rings 70. Eachconcave site 61 is defined by the arc-shaped outer circumferential faces73 of adjacent pocket rings 70 and an edge face 81 of the rear face sideof the connecting portion 80. The bottom of the concave site 61 is theedge face 81, which is closer to the pocket opening 72 b than the bottomportion 72 a of the pocket 72 is to the pocket opening 72 b. Further,the thickness of the pocket ring 70 decreases on moving around thepocket 70 from the bottom portion 72 a to the nail portion 71.

Each of the two rows of bearings 50 is mounted with a respectiveretainer 60. The bearings 50 are snapped in between each rotation groove31 of the outer ring 30 and the respective rotation grooves 11, 41 ofthe shaft 10 and the inner ring 40. As shown in FIG. 1, each retainer 60is oriented such that the pocket openings 72 b of each retainer 60 areopposed to each other. After mounting each retainer 60, grease isinserted into each concave site 61 from the rear face side of theretainer 60.

Edge face 81 of connecting portion 80 forms the bottom of the concavesite 61 on the rear face side of the retainer 60. This edge face 81 isnearer the pocket opening 72 b than the bottom portion 72 a of thepocket 72 is to the pocket opening 72 b. as shown in FIG. 3. In otherwords, the concave sites 61 are deeply scooped out of the rear-face sideof the retainer 60. Further, because the thickness of the pocket rings70 decreases going around the pocket ring 70 from the bottom portion 72a, through the connecting portion 80, to the nail portion 71, thecircumferential length 73 of the concave site 61 may be increased ascompared to the length for a uniformly thick pocket ring 70.

With this configuration, a relatively large quantity of grease may beinserted into and held in the concave site 61. As the retainer 60revolves around the shaft 10, the pocket 72 may receive adequate baseoil from the grease at the bottom of the concave site 61, i.e. edge face81, to lubricate the bearings 50 because the edge face 81 is nearer tothe pocket opening 72 b as described above. Moreover, the greaseinserted into the concave site 61 does not easily adhere to the outerring 30, the inner ring 40, the shaft 10, and the shield 51. Thus baseoil may lubricate the bearings 50 immediately upon the rotation of theshaft 10, increasing the life span of the shaft bearing 20 andpermitting the rotation with low torque.

FIG. 4 is a partial magnified side view of another preferred embodimentof the retainer 60B. The retainer 60B includes planes 75 formed on theedge portions of the outer circumferential face 73 of the pocket ring 70that forms the concave site 61, towards the center 74 of the pocket ring70. This embodiment of the retainer 60B may be manufactured by injectionmolding of resin into metal molds. If the two metal molds separateaxially, i.e. separate axially along a circumferential line, the moldsmay be simplified by matching the parting line of the molds with theedge face 81, or having the parting line of the molds cross the planes75. Further, the pouring gate of the mold may be set on the edge face 81on the rear face side of the retainer 60B.

FIG. 5 is a partial magnified side view of yet another preferredembodiment of the retainer of 60C. The retainer 60C includes a channel84 between the edge faces 81, 82 of the connecting portion 80. Thechannel 84 is formed on the outer circumferential face 83 of theconnecting portion 80. Grease is inserted into the concave site 61 andis held in the channel 84. The channel 84 supplies base oil to theinterior of the pocket 72, improving lubrication of the bearing 50 thatis snapped into the pocket 72.

In general, the present invention permits the introduction of largequantities of grease onto the rear face side of the retainer 60–60C,opposite the pocket opening 72 b side of the retainer 60–60C, forlubricating the bearings 50 and rotation grooves of the shaft bearing20. It should be understood, however, that the present invention is notlimited to the embodiments described above and that other configurationsof the concave site 61 are possible for holding grease in closeproximity to the pocket opening 72 b, such as closer to the pocketopening 72 b than the bottom portion 72 a of the pocket 72.

The foregoing detailed description is merely illustrative of severalphysical embodiments of the invention. Physical variations of theinvention, not fully described in the specification, may be encompassedwithin the purview of the claims. Accordingly, any narrower descriptionof the elements in the specification should be used for generalguidance, rather than to unduly restrict any broader descriptions of theelements in the following claims.

1. A shaft bearing retainer comprising: at least two pocket rings, eachring having a circumferential outer surface, an opening, two nailportions located immediately adjacently to the opening, and a rearportion located opposite the opening; and at least one connectingportion disposed between adjacent nail portions of the two pocket rings,wherein the connecting portion and circumferential outer surfaces of thepocket rings form a concave site, wherein a bottom of the concave siteis positioned closer to the openings of the pocket rings than bottomportions of the pocket rings are to the openings of the pocket rings,and wherein the thickness of each pocket ring gradually decreases suchthat the thickness of each pocket ring in a middle section of the rearportion is greater than the thickness of the rear portion in sectionsadjacent the connecting portion.
 2. The shaft bearing retainer of claim1, wherein each of the pocket rings further comprises an inner surfacehaving a shape complementary to the shape of a rolling element of theshaft bearing.
 3. The shaft bearing retainer of claim 1, wherein theconcave site is configured to accommodate lubricating material.
 4. Theshaft bearing retainer of claim 1, wherein each nail portion isdeformable towards the opening of the pocket ring.
 5. The shaft bearingretainer of claim 1, wherein the retainer is composed of a deformableelastomeric material.
 6. The shaft bearing retainer of claim 5, whereinthe elastomeric material is resin.
 7. A shaft bearing having a retainer,wherein the retainer comprises: at least two pocket rings, each ringhaving a circumferential outer surface, an opening, two nail portionslocated immediately adjacently to the opening, and a rear portionlocated opposite the opening; and at least one connecting portiondisposed between adjacent nail portions of the two pocket rings, whereinthe connecting portion and circumferential outer surfaces of the pocketrings form a concave site, wherein a bottom of the concave site ispositioned closer to the openings of the pocket rings than bottomportions of the pocket rings are to the openings of the pocket rings,and wherein the thickness of each pocket ring gradually decreases suchthat the thickness of each pocket ring in a middle section of the rearportion is greater than the thickness of the rear portion in sectionsadjacent the connecting portion.
 8. The shaft bearing of claim 7,wherein each of the pocket rings further comprises an inner surfacehaving a shape complementary to the shape of a rolling element of theshaft bearing.
 9. The shaft bearing of claim 7, wherein the concave siteis configured to accommodate lubricating material.
 10. The shaft bearingretainer of claim 7, wherein the retainer is composed of a deformableelastomeric material.
 11. The shaft bearing retainer of claim 10,wherein the elastomeric material is resin.
 12. The shaft bearing ofclaim 7, wherein each the nail portion is deformable towards the openingof the pocket ring.